Wet bathroom floor due to leak - PigletJohn? (sorry v. long)

We have a flat which we rent out. It used to be the laundry room for the block - has walkway underneath and no-one above us. It is a concrete construction. When we lived there, we had persistent problem with damp on one of the bedroom walls. We insulated that, put in larger radiator and had a dehumidifier.

We have had various tenants and most are not good at following the rules... open windows, heating on (obviously not at the same time!) and keep dehumidifier on. A couple of months ago we had a leak in the bathroom, well several actually. Had various plumbers round - one said it was the toilet and fixed it, also, the shower screen leaking - fixed that. Dh found a leak under the bath and sorted that out. Water was pouring from our flat on to the walkway beneath - down the side of the wall. This is no longer happening, however the floor of the bathroom is wet - a sheen of water every day and the hall outside. The toilet is on the wall adjoining the hall - have a tide mark on the paintwork in the hall. We are assuming this is from the leaking toilet.

A friend (builder) looked and he said the overflow from the bath was leaking - current tenants have full baths - and he sorted that out. He thinks it is just so wet underneath the bath and will need time to dry out. Does this sound right? What about getting an industrial dehumidifier? Is there anything we can do to speed up drying out?

We had the bathroom gutted and new one installed 4 years ago...i don't think they did a good job as we have so many leaks a few years on.

tying dry kitchen roll round all pipes and wastes will show up water. Lay it under the bath and the edges of the bath and basin and around the WC. You will get condensation on the cistern from the damp air.

If the leaks really are cured, then the concrete (presumably) floor and the walls will be wet. A dehumidifier (with the door and window shut) will dry them out in a couple of weeks. If it is a small room you might not need a big builders one (about the size of a washing machine with a powerful fan) but you could buy one. I don't think they are generally safe in bathrooms, see if it has an IP rating of 44 for higher. Big dehumidifiers have a water pump and hose to expel the water down a drain. The water will be dirty enough to stain a bath.

Fans blowing air onto the wet walls and especially the floor will help evaporate off the surface. Take up all floor coverings. If anything in the bathroom is made of chipboard or mdf, take it out and put it on a bonfire.

you might be able to get the insurance co to contribute to drying out.

When you think it is dry, it won't be really. An effective centrifugal extractor fan, running night and day, will gradually remove the residual moisture in a few more months. You can run it at the same time as the heating. It will run for about 50 hours on 14p worth of electricity. I am always stunned by people who refuse to use extractors on grounds of cost.

Thank you so much. Builder friend said it was so wet that it was difficult to tell if it was wet due to old or new water, he didn't suggest kitchen towel though, so thank you for that. Basically, apart from the ceiling, the bathroom is tiles on concrete.

It is very difficult as we don't live there. I don't think she puts the dehumidifier on even in this situation.

We have had a nightmare with various plumbers and just don't know who to trust.